Notes on “The Last Generation” (F. Pearce)

Pearce, Fred – The Last Generation: How Nature will take her Revenge for Climate Change (2008) PDF
Category: global warming; Rating: 5/5
Summary: Amazon reviews

Another excellent book on climate change that goes beyond the conservative conclusions of the IPCC reports, with the emphasis here being on change that happens with speed and violence after the crossing of certain tipping points, in contrast to the IPCC’s gradualist approach. Since Lynas covered most of the catastrophic climate change scenarios in his book Six Degrees (on which I made notes here), I will only be covering select chapters from this book – mostly those that add more detail to the most significant feedback trends, and original ones that dwell on unexplored territory like the influence of clouds and aerosol pollutants on warming and more exotic possibilities like a hydroxyl collapse. When reading this, it is a good idea to keep this useful conversion: 1 ppm by volume of atmosphere CO₂ = 2.13 Gt C, in mind. To keep things in perspective, current anthropic emissions stand at 8bn tons of carbon a year; atmospheric CO2 levels are increasing by around 2ppm a year, the rest still being absorbed by the biosphere (though as we shall see this state of affairs may not last long).

I repeat the disclaimer that since I am doing this mostly for myself as part of my research into my book on “future history”, I cannot guarantee this will be interesting.

Introduction. Though calling himself a “skeptical environmentalist”, Pearce believes the global warming story adds up – “nature’s revenge for man-made global warming will very likely unleash unstoppable planetary forces. And they will be sudden and violent”. According to NASA climate scientist James Hansen, “We are on the precipice of climate system tipping points beyond which there is no redemption”.

The Watchtower: Keeping Climate Vigil on an Arctic Island. The ostensibly pristine High North is paradoxically one of the most polluted places on Earth. It rains mercury, concentrates pesticides from Asia and the air is filled with acid fogs from Siberian factories.

Ninety Degrees North: Why Melting knows no Bounds in the High North. The Arctic is melting fast, being 40% thinner in the 1990′s from the 1950′s. Though melting takes a lot of energy, once complete the Sun warms the water left behind, which is darker and more heat-absorptive than the surrounding ice and hence warms more rapidly, heating the air around it. As such, melting is a threshold process. An immense pulse of warm water since 1999 burst through the Fram Strait (between Svalbard and Greenland), and worked its way through around the shallow continental shelves that circle the Arctic Ocean. Hours after reaching the Laptev Sea, the temperatures rose by 0.5C and since then it has stayed ice free in 2004. (AK: Is this water that previously disappeared down the Arctic chimneys?). Once the Arctic melts, the ice-albedo effect will accelerate warming and the reduces temperature differentials between the tropics and the Arctic will destabilize current air and ocean currents.

On the Slippery Slope: Greenland is Slipping into the Ocean. In lower Greenland behind the equilibrium line marking zero net ice gain, small melt-water lakes are accumulating and flowing down crevasses called moulins, with waterfalls of up to 3km high taking the water to the bedrock of the ice below (AK: That would be higher than Angel Falls in Venezuela!). And during warm years the km-thick ice sheet actually lifts off the bedrock and floats on the water, rising by half a meter or more! These lakes are like pots of magma beneath volcanoes – “more melting will mean more lakes in some places, more water pouring down crevasses and more disintegration of the ice”.

Glaciers are thinning and speeding up, with Jakobshavn losing 50cu km a year (equal to that of the Nile). Though it currently exits below the water line through submarine valleys via giant floating ice shelves that buttress them, as the oceans warm these shelves will themselves thin and collapse. “The picture, then, is of great flows of ice draining out of Greenland, lubricated by growing volumes of melting water draining from the surface to the base of the ice sheet and uncorked by melting ice shelves at the coast”. This nonlinear response implies an exponential increase in ice loss for the future; though conventional wisdom says they will take centuries to melt, it could in as little as several decades.

The Shelf: Down South, Shattering Ice Uncorks the Antarctic. Disintegration of Larsen B in 2002 – at the height of summer, melting snow formed ponds that put pressure on crevasses, wedging them open (water is denser than ice) and instigating the catastrophic collapse of 500bn tons of ice, releasing thousands of large icebergs. Other ice shelves are also in increasing danger, including the Ross and Ronne ice shelves. Though they of themselves won’t raise sea levels, since they are already floating, they do buttress the glaciers that feed them – like uncorking a champagne bottle, the “glaciers that once discharged their ice onto the Larsen B shelf are now flowing into the sea 8 times faster than they did before the shelf collapsed”.

The Mercer Legacy: An Achilles’ Heel at the Bottom of the World. West Antarctica is vulnerable since it is “perched precariously on an archipelago of largely submerged islands”. Though apparently safe since it is buttressed on two sides by mountains, and on the other two sides by the Ross and Ronne ice shelves. Yet if they were to give way, the entire shift could lift off and float away – once begin, disintegration may be catastrophically rapid.

It has a “weak underbelly” in Pine Island Bay, a large inlet on the Amundsen Sea. It is an outlet for two of Antarctica’s top five glaciers: Pine Island and Thwaites, which drain 40% of W. Antarctic ice sheet and are already the greatest contributors to global sea level rise. The surrounding ice shelves melt faster due to warmer waters; in turn, the two glaciers drastically accelerated. As ice shelves thin, more water penetrated beneath glacier…the “grounding line” is retreating 2km a year. Furthermore, inland amongst its tributaries the PI glacier sits on great lakes of melt-water. If the area they drain all melts, sea levels will rise by 1­2m. Thwaites taps into vast reservoirs of ice in the middle of the ice sheet…may drag them along with it. If you pull the plug, ice goes faster and there is thinning…will the plug reform further back, or will the ocean deliver enough heat for it to just blowtorch its way to the center? If the latter, the W. Antarctic ice sheet could collapse within the century.

In the East Antarctic, the Totten glacier drains an area with more ice than in the entire W. Antarctic. Since early 1990′s, catchment is losing enough ice to lower its height by more than 10m annually (despite raising ice levels in the flatter interior). Cook glacier is doing the same. Furthermore, like Pine Island and Thwaites, their grounding lines (farthest point downstream where ice makes contact with solid rock) of Totten and Cook is below sea level – by more than 300m in Totten’s case. Again “warmer waters appear to be loosing that contact. Should the grounding line begin to retreat, we can expect the glacier to begin
the familiar process of thinning and accelerating”.

In the Jungle: Would we notice if the Amazon went up in Smoke? The Amazon is the largest living reservoir for CO2 on the land surface of the Earth, with its trees and soils each containing 70bn tons of carbon. (AK: for comparison, human emissions constituted 8bn tons in the mid-2000′s, around half of which was absorbed). Unfortunately, the forest is fragile and is now believed to be “close to a tipping point beyond which  it will suffer runaway destruction in an orgy of fire and drought”. An experiment shows it can only handle two years of drought, with the trees extending their roots and slowing their metabolism; yet by the third year, the amount of stored carbon plummets by 70%. For starting with the tallest, trees begin dying with the tallest – exposing the forest floor to the drying Sun. Fires will begin, creeping low along the forest floor – no huge flames burst through the canopy and the fires are largely invisible to the satellites keeping a constant watch overheat. But many trees die, their bark scorched and the flow of sap from the roots staunched.

The Amazon is now a significant CO2 source and is gradually drying. It will not be able to recover beyond a certain point, ushering in the “savannization” of the Amazon. There was already a big drought in 2005 – killing trees, triggering fires and reducing the Amazon’s moisture recycling ability, thus increasing the probability of a future drought – caused by extremely warm temperatures in the tropical Atlantic (which also caused the big hurricane season, including New Orleans). In the future, starting from the vulnerable north­east, the rainforest dies and “ceases to recycle moisture back into the atmosphere to provide rainfall downwind”, resulting in a “wave of aridity” which travels west and culminates in a “mega­fire event”, in which rainforest turns to desert and carbon is released back.

The Amazon creates rain not just for itself, but for others – half of its moisture is exported to the south to water the pampas grasslands of Argentina [AK: an agricultural breadbasket], the Andes [AK: once it ceases, this results in accelerated glacier melting there on which Lima depends], southern Africa and the Caribbean. Also, the moisture carries energy; solar energy evaporates water off the forest canopy (hence the reason forests are cooler than the surrounding plains) and condenses it into clouds, releasing energy back into the air to power weather systems and high-­level winds called jets far into the northern hemisphere. This drives winter storms across North Atlantic towards Europe; once the rainforest expires, the hydrological engine sputters to a halt, leading to dessication in Europe.

Wild Fires of Borneo: Climate in the Mire from Burning Swamp. In 1997, a record-­breaking intense El Nino event in the Pacific stifled the storm clouds that normally bring rain to Borneo and the Indonesian islands. Landowners burned swamp forest to plant palm oil and other profitable crops, resulting in one of the greatest forest fires in human history. The deepest burning was in central Borneo, where “the fires had burrowed down, drying and burning a vast peat bog that underlies the forest” ­ which lasted for several months.

This was partly due to an early 1990′s decree by Suharto to settle the area, drain the swamps and make rice paddies to achieve food self­-sufficiency. Though this project failed because the soils were infertile, the 4000km of canals built for this purpose continue draining the swamps. The now dessicated peat burns every dry season, especially during strong El Ninos.

At least half the world’s are on Borneo, Sumatra and West Papua; they are especially concentrated in central Borneo. They contain 50bn tons of carbon, almost as much as the Amazon. During the El Nino events of 1997-98, the smoldering swamps lost 0.8­bn – 2.6bn tons of carbon into the atmosphere. US research showed 2bn tons more carbon than usual entered the atmosphere in 1998, some 2/3 of originating in SE Asia. Farmers in Borneo continue burning forest to clear the land for farming.

Sink to Source: Why the Carbon Cycle is set for a U-­Turn. Though the 1970′s – early 1990′s saw greater carbon uptake due to the fertilization effect of great CO2 concentrations, its power as a sink leveled off in 1993 and went into dramatic decline after the mid-1990′s as it became dwarfed by deforestation, dessication and decay. Examples: major fires in Borneo and Siberia in 1998; the European summer heatwave of 2003, which released 0.5bn tons of carbon over 2 months. So as the century progresses, in Europe, higher CO2 uptake in early spring is canceled out greater heat and watter stress during hotter, drier summers. Even in the High North the overall effect is diminishing, despite the advance of forests north (if they don’t fall prey to new plagues of insects).

Why? During the 1970′s – 1980′s, the increased CO2 temporarily led to an increased fertilization effect, with a time lag before it was translated into higher temperatures; now the temperatures are catching up, resulting in decay coming close to outstripping growth and absorption. The biosphere will go from being a negative to a positive feedback, eventually releasing 7bn tons of carbon a year – roughly equivalent to current anthropic emissions. Even today Britain is releasing 13mn tons of carbon a year, around 1% of its carbon store and canceling out all its efforts to comply with Kyoto.

The Doomsday Device: A Lethal Secret stirs in the Permafrost. The West Siberian landscape: scarred by human activity (fragmented by pylons, seismic routes, railways and pipelines), littered with industrial detritus (abandoned drums, pipes and cables) and wreathed in black smoke from natural gas flares. The accelerated Arctic warming is moving the permafrost boundary north, melting peat bogs and increasing decomposition rates. As the thawed vegetation rots, its carbon will return as CO2; but in the bogs and lakes without oxygen, it will be converted into methane gas by anaerobic bacteria. As temperatures get warmer, emissions rise exponentially. There is around 450bn tons of carbon locked up in the peat bogs of the Far North, a third of the all the carbon locked up in the world’s soils. If released at once as CO2, it will raise temps by 3C; if as methane, by tens of degrees – making it a Doomsday Device. (Fortunately, methane breaks down into CO2 after a decade or so).

The Acid Bath: What Carbon Dioxide does to the Oceans. Since the Industrial Revolution, the oceans absorbed 120bn tons of carbon, and are absorbing some 2bn more every year. It was a major see-saw governing the transitions between Ice Ages and interglacials. During colder periods, the land is cold and dry, and dust storms transport large amounts of minerals that fertilize the cold­-loving plankton (during last Ice Age 120bn tons of carbon moved from land and atmosphere to the oceans), forming a powerful negative feedback. Since warmer, more acidic oceans kill calcerous life forms (e.g. dissolves shells of pteropods, making them vulnerable to predators), the ocean will stop being a sink.

The Wind of Change: Tsunamis, Megafarts and Fountains of the Deep. Methane hydrates: “They are generally close to the surface of the ocean floor but frozen – confined not by physical barriers but by high pressures and low temperatures – in a lattice of ice crystals rather like a honeycomb”, and ­ probably form when cold ocean water meets methane created by microbes living beneath the sea bed. Usually just beyond the edge of continental shelves, many tap into even larger stores of gaseous methane beneath, where heat from the Earth’s core keeps them from freezing. Though today’s waters are colder than during the PETM, they are warming much faster – if so, “the trigger on the clathrate gun will be a lot touchier than it was 55mn years ago”.

Effects. Ships just sink flat (water becomes much less dense when saturated with methane bubbles; less buoyant), like at Witch’s Hole and Bermude Triangle? Methane releases lead to cascading submarine slides and tsunamis. Methane hydrates have been found on Black Ridge off eastern US, in the Barents Sea southeast of Svalbard, north side of Storegga Slide (site of past tsunami). Another hotspot (pardon the pun) is the northern coast of Spitzbergen, which is warming fast as warm water currents break through the Fram Strait into the Arctic – in an ancient slide, the cliff face there fell by 1400m, seven times more than at Storegga.

The situation is now similar to the past – fast ­rising sea temperatures penetrate sediment and defrost the frozen methane. Global warming leads to more blowouts, more craters, more releases – perhaps a tsunami crashing into Europe at the same time as a big methane outburst pushes climate change into overdrive. At least it will take centuries, right? But clathrates are sometimes found close to surface, especially in the Arctic; also, “seabed sediments often contain cracks that extend into the frozen clathrate zone. Warm water takes no time to penetrate the cracks and can quickly unleash the methane”. Oops.

What’s Watts?: Planet Earth’s Energy Imbalance. Currently there is a global energy imbalance, as Earth transitions into a warmer state. (Equilibrium is when absorption = radiation into Space). The growing energy gap is without precedent. Net warming is now going into heating the lower atmosphere and the oceans, the latter of which take the lion’s share because of their greater heat capacity. This means are there time lags – the oceans are deep and it will take a millennium to heat them fully; the current warming has only penetrated the top 750m. As this pulse progresses, the “oceans [will be] draining more heat out of the atmosphere than they will once the oceans atmosphere return to a long­term balance”.

Perhaps around 0.6C of warming is lopped off by the oceans – half of it will come within 30-40 years of atmospheric CO2 stabilization, and the rest over many more decades and centuries. The current 2% heat share accruing to melting ice is to increase, as melting becomes explosively rapid – resulting in faster sea level rise, reduced albedo and further accelerated temperature rise. [AK: once Antarctica starts melting bigtime, most energy goes to melting that ice – ocean surfaces may not warm so much. Good for fisheries, bad for hurricanes! Yeah! BUT bad for monsoons. So S. Oceans cool, switching currents to there (see last), while Arctic warms?].

When the ice sheets covered a third of the northern hemisphere,the  vast expanses of white raised the planet’s albedo, resulting in an average decrease of solar heating of the Earth’s surface by 4 watts / sq m. Now this will reverse. If the planet’s albedo drops by just a tenth, to 27%, that will be comparable to a 5x increase in CO2 concentrations! Especially in the Arctic, the albedo effect will become absolutely dominant.

Clouds from Both Sides: Uncovering Flaws in the Climate Models. Though most climate models predict 3C of warming during the century, some tend to as high as an apocalyptic 12C! There are three main things to climate models – ice, CO2 and water vapor, with the last one’s effects relatively unknown. Though it is known water vapor by itself amplifies the effects of CO2, the contributions of clouds are a big unknown.

During the day, clouds shade us from Sun’s rays and keep the heat down, but at night they offer an insulating blanket. This effect is most pronounced in deserts. Different clouds work in different ways – wispy, high cirrus clouds are good at absorbing Sun’s heat and re­radiating it below (AK: similar to contrails!); the low, flat stratus clouds of a dreary summer day keep the world cool. Currently, the net effect is neutral or even slightly cooling – though no­-one knows for sure, even a slight change in global cloud patterns can substantially affect the world’s albedo.

When the world warms, there will be more water evaporation and presumably clouds, making the world cooler. But the increased heat also burns off clouds faster, leaving behind blue skies. As such, clouds may end up forming, filling up with moisture, raining out and dissipating faster – perhaps the fluffy, long-lasting cumulus clouds of today will metamorphose into dark, short-lasting cumulonimbus clouds.

Especially in the tropics, there has been a trend towards clearer skies, for since the mid-1980′s the tropical convection processes that caused air to rise when the Sun is at its fiercest have intensified and storm clouds form and grow more quickly where the warmed air is rising (PS. The reason hurricanes are most intense in the tropics). Since these clouds rain out more quickly, the tropics turn drier and less cloudy. The main difference between the old models and the new scary models are in how they incorporate cloud feedbacks.

There is increasing haze and aerosols emissions from industrializing Asia (smoke, soot, dust, and highly-reflective sulphate particles). Though they both absorb and radiate, the overall effect is highly cooling – meaning that at times central Europe, the plains of India, the Amazon, and eastern China miss out on GW. This means that part of global warming has been masked by the cooling effect of aerosol pollution!! But as these nations get richer (or face industrial collapse, like post-Soviet Eastern Europe), they will expend efforts to clean up this mess to avoid the smogs and acid rain, and GW will hit with full force.

The big question is – how tightly is the spring coiled? Introducing these effects into the equation, the new range from doubling CO2 levels is a 6-­10C temperature rise, well outside the bounds of imagination. Furthermore, even barring their negative side effects the use of aerosols to stem global warming cannot be a permanent answer – unlike CO2, which accumulates in the atmosphere for centuries, aerosols are washed out of the atmosphere in mere days.

Other uncertainties. Though sulphate particles undoubtedly cool things, there’s uncertainty about soot (black carbon from incomplete burning of coal, biomass, diesel). It warms the surrounding air, but shields the ground underneath – so the net effect is intense local cooling coupled with overall warming.

A Billion Fires: How Brown Haze could turn off the Monsoon. Due to the millions of ill-maintained diesel burning buses and two­-stroke rickshaws plying its gridlocked streets, sulphur dioxide emissions from coal-­burning power stations and inefficient cooking stoves in the countryside, there is now a near-constant smog during the winter months over the north Indian plain. This “brown haze” now encompasses much of Asia. Even half a world away in Svalbard, “soot is falling out onto the snow and ice, making the white surface darker” and helping melt the Arctic ice cap.

Smoke emissions rural cooking stoves produce 1­2mn tons of aerosols a year, including 0.25mn tons of soot, making them responsible for 40% of India’s aerosol emissions! This reduces solar radiation reaching India’s surface by 22 watts / sq m, supposedly enough to cause massive cooling; BUT only 7 watts is lost entirely, since other 15 watts / sq m is backscattered into space – absorbed by the soot in the aerosols and reradiated, heating the atmosphere. In winter, it counteracts GW and cools the air across India by an average of 1.5C; in summer, when the pollution is rained out and skies are clearer, temperatures rose by 0.5C in line with the global average.

This cooling “delays the heating of the land that stimulates the monsoon rains”, which are vital for feeding 3bn people in Asia. They’ve increased in the traditionally wetter south, where the haze is less strong; and decreased in the north, where the haze is thickest. There is a similar situation in CHina, but where more of the pollution is in the form of sulphate particles from burning coal – the most polluted areas saw declines of 0.6C, altering rainfall patterns. Monsoons have become greater in the south and weaker in the parched north – not surprisingly, since “when climate models are programmed to include a strong Asian brown haze many of them produce strong rainfall in southern China, coupled with near ­permanent droughts in the north”

Forest burning in the Amazon and Africa to clear lands plays havoc with the atmospheric circulation – rainfall is reduced; aerosols stay in the air for longer; the upper atmosphere becomes wetter due to buildup of water vapor; it forms intense thunderstorms (“hot towers”), causing hail storms! More water vapor in stratosphere → more ozone destruction. According to climate models, soot emissions over India and China can trigger drought in the African Sahel and warming in western Canada.

Hydroxyl Holiday: The Day the Planet’s Cleaner didn’t show up for Work. Hydroxyl (OH) is created when UV bombards gases like ozone and water vapor; as soon as it’s created, it reacts with other molecule, mostly polluting substances, and is gone within a second. It is very rare, having an atmospheric concentration of less than 1ppt. Hydroxyl is the “atmosphere’s detergent”, reducing gaseous pollutants so they’re soluble in water and wash away in rain (oxidation), like converting SO2, which would otherwise clog the air for months, into acid rain that quickly falls to Earth. CO and CH4 are oxidized to CO2, or to NO2. The one pollutant it doesn’t affect is CO2, hence its relatively long life­time in the atmosphere. [AK: so if it disappears and stops washing out aerosols like sulphate particles, this could lead to global cooling].

Concentrations of hydroxyl much higher over the warm air in the tropics, where UV radiation is most intense, and close to non­existent in the Arctic, where despite the ozone holes there is usually little UV to make more hydroxyl. So “toxic chemicals that might survive for only a few days in the tropics will last a year or more in the Arctic air”. This is one reason why pollutants like acid hazes and pesticides accumulate in the Arctic.

Since it’s destroyed when oxidizing pollution, it may be getting overworked. Joel Levine suggested in the 1980′s there was a 25% reduction in hydroxyl over the previous 30 years. Not surprising, since it spends a lot of its time oxidizing carbon monoxide (emitted by forest fires, fossil fuel burning and small domestic stoves), concentrations of which TRIPLED worldwide during the 20th C.

Sasha Madronich – ­ “under high pollution, the chemistry of the atmosphere becomes chaotic and extremely unpredictable. Beyond certain threshold values, hydroxyl can decrease catastrophically”…many urban areas are “already sufficiently polluted that hydroxyl levels are locally suppressed”. Why? The sheer volume of pollutants and smog prevents UV light from penetrating into the air to create more hydroxyl. Ironically, not only more pollution, but also a thicker ozone layer, nature’s filter versus UV, will have the same effect.

The Big Freeze: How a Wobble in our Orbit triggered the Ice Ages. 100,000 year cycles of Ice Ages and interglacials, with rapid switchings back and forth (Agassiz). During Ice Ages, the world was covered in ice – sea levels were 120m lower and ice sheets were 4km high and covered 30% of the Earth’s land area. Temps fell by 5C globally. Beyond the ice sheets, the world was dry and cold – deserts covered the Mid­West, France and the lands between Germany and Mongolia; the Sahara expanded; the Asian monsoon largely vanished; the tropical rainforests of Africa and S. America contracted to a few refuges surrounded by sparse grasslands.

Eccentricity, inclination and precession. First governs the Ice Age cycles; other two trigger short warm episodes during Ice Ages (Croll & Milankovitch). Since actual change due to wobbles is small, there exist “powerful embedded amplifiers that can make it highly sensitive to relatively small changes” – 1) ice-­albedo effect (cold summers melted less ice and kicked world into inreasing ice cover, albedo and cooling, and 2) as deserts spread, the cold winds blew off nutrient-­rich dust into the oceans, feeding plankton, which love cooler seas and sequestered carbon down from 600bn tons to 400bn tons (now 800bn tons and counting) in the atmosphere. Even today main constraint on plankton growth is lack of iron (AK: hence the ideas for iron seeding the world’s oceans for geo­engineering). Two other feedbacks: dried up wetlands → fewer methane emissions; less water vapor → amplified cooling. This history demonstrates the sheer power of feedbacks.

The Ocean Conveyor – The Real Day After Tomorrow. The ccean conveyor = thermohaline circulation = meridional overturning circulation. The Gulf Stream → waters cooled in N. Atlantic by cold Arctic winds in winter; becomes saltier due to ice formation → becomes heavier → sinks to seabed and takes 1000­year journey round the world → resurfaces in S. Atlantic → returns to the Gulf Stream. Due to hotter Arctic temps, which lead to more Greenland melting, increased precipitation and runoff from rivers, the current may shut down suddenly.

Though the Labrador Sea cold flow is still OK, the flow from where the vanishing chimneys were has halved. Measurements suggest that the strength of Gulf Stream is down by 30% since the mid­-1990′s, so perhaps a Little Ice Age will be on the way once the Arctic sees substantial melting. However other measurements refute this and a big cooling trend is seen as unlikely (can instead lead to increase in floods and storms, more frequent and intense El Nino events, ocean anoxic event).

More Climate History: Very Brief Summaries

Arctic Flower: Four fluctuations during the last glacial­interglacial transition, probably caused by release of meltwater into North Atlantic, breakdown of Gulfstream and associated cooling – particularly during the four Dryas periods.

The Pulse: Medieval Warm Period (only in Europe – Mayan collapse due to drought, Anasazi, etc) and Little Ice Age (subsistence crisis throughout much of Europe – also abroad, like Greenland Viking collapse, Ming China collapse, Amazon drying, floods washing away Timbuktu). 1500 year cycles of flunctuating heat based on solar pulses – shows what a big amplifying effect the Earth can bring to bear, and as such the extent of change brought about by global warming.

The Fall: Sahara was savanna some time back, when Earth’s orbital path was more favorable, as was Arabian Peninsula – hence the big groundwater reservoirs there. Increasing droughts in 21st C – all the American West, Central America → Iraq / Arabian Peninsula, Mediterranean Europe. Strong El Nino → aridity over West N. America. Megadrought or Garden of Eden? Probably longer and more intense droughts, interspersed with brief, intense storms and floods.

See­Saw: The Sahara greens the Amazon – dust blown off travels across the Atlantic Ocean and fertilizes the Amazonian rainforest. If the Sahara becomes wetter, this effect will diminish.

The Dance: Poles or the Tropics? Who leads in the Climate Dance?: A major division amongst climatologists. Work towards synthesis. Polar view: orbital changes → ice albedo → cooling → oceans sequester more carbon → ocean conveyor shuts down → Ice Ages. Tropical view: tropics are where due to heat much of the global dynamics are made…poles are where major feedbacks kick in: ice albedo, permafrost, and alterations to ocean currents.

A Chunk of Coral: Probing the Hidden Life of El Nino. What is El Nino? During normal times, driven by the Earth’s rotation the winds and surface waters of the tropical Pacific flow from the Americas in the east to Indonesia in the west; a pool of hot water accumulates on the ocean surface again the Indonesian archipelago, which is 40cm higher than further east and up to 8C warmer than surroundings (the “firebox” – ­ like the N. Atlantic chimneys, it has a propensity for threshold change via El Nino / La Nina system)

The effects: drying Australia; drenches normally arid Pacific islands, reaching coastal deserts of the Americas; disrupts Indian monsoon; drought in the Amazon; affects African monsoon and flow of the Nile (depending on season); triggers rain in the hills of Palestine; damps hurricane formation in the N. Atlantic. It lasts 12 to 18 months, after which it goes into sharp reverse called La Nina – wet conditions in Indonesia, fierce drought further east.

Historically, El Nino appeared during cold conditions (end of Ice Ages, Little Ice Ages) and La Nina (medieval warm period) during hot conditions. The same precession shift that desertified the Sahara (colder conditions), also coincided with an increase in El Nino frequency from once every 15 years to once every 6. BUT, coral records show that El Nino has increased since the mid­-1970′s to once every 3.5 years. This affected the rich, cold­current sustained fisheries off the Peruvian coast, for since 1976 the cold current was pushed to ever greater depths, even during normal times – the system has been stuck in a quasi-­permanent El Nino state.

Really? Yes. In 1982-­83 there was most severe El Nino in the 20th C – you wouldn’t expect another such for 100 years, but in 1997­98 there was an even larger one, and minor ones in 2002 and 2004. The traditional El Nino is thought to no longer be sufficient to handle and redistribute the larger degree of warming and heat in the system. Models indicate that in the 21st C, cold La Nina’s will happen occassionally and with greater intensity; but they will be breakout events, while the normal situation will become more El Nino-­like.

[AK: big uncertainties, of course – since warmer periods historically indicated La Nina and colder periods favored El Nino. But note that it might have more to do with solar intensity patterns: in African Humid Period, the Sun blazed down square on Sahara, raising the hot air and generating a strong monsoon over it. It desertified when this heating stopped – perhaps the focus moved further south, where it warmed the SE Asia Ocean more even as it the world cooled / said ocean hottened up relative to its surroundings? What about the Asian Brown Haze – does it extend that far, and could it shift the focus of this system?]

Feeding Asia: What Happens if the Rains Fail? The monsoon – during winter, cold, dry winds blow from the Himalayas and Asia is mostly waterless. During summer, the land heats quickly, hot air rises, moist ocean air rushes in and farmers grow their rice that sustains 3bn people.

Unfortunately, strong El Nino’s tended to switch them off as they draw heat away from Asia. The trend appears to have broken since 1970′s, when El Ninos strengthened but the monsoons remained steady. What will happen later?

The strength of monsoons is also correlated with heat in the N. Atlantic. But which one is dependent on which – or did they both depend on the solar pulses? Theory that warm Atlantic sends warm winds to provide earlier melting of the Tibetan plateau – so if the melt starts earlier, then monsoon will be longer and more intense. So if the Atlantic conveyor fails, effects may be even worse for Asia than for Europe.

BUT according to the tropical school, the tropics affect both – cooling of the tropics both sends less warm water to the Gulf Stream and diminishes the Asian monsoons. Will certainly be different from history since 1) before changes were based on solar fluctuations, now on CO2 inputs and 2) complicated by Asian brown haze which cools the land.

Ozone Holes in the Greenhouse: Why Millions Face Radiation Threat. History – CFC’s (chloride form) used, will take 100 years to heal – if the international commitments are kept. (But if bromide variants were used, which is 100x more effective at destroying ozone, then probably the whole Earth would now suffer from an ozone hall). For ozone holes to form, you need temperatures of ­90C or less (to form polar stratospheric clouds) and sunlight – happens sometimes over Antarctica and even the Arctic.

Though ozone holes have been contained by the 1990′s and are gradually healing, global warming means the stratosphere is getting colder as (more heat is re­radiated into space) – especially over the areas with the most severe warming, like the Arctic! Also there is more water vapor in the stratosphere as stronger convection currents drive thunderclouds higher, which makes it easier for polar stratospheric clouds to form. Hence ozone problem may get worse before it gets better.

[AK: that said, I don't think cancer effects will be that bad – no high incidence amongst Inuit, for instance. BUT, northern populations lead lifestyles that predispose them more to chronic diseases – so ultimately uncertain. But ordinary life will probably be mostly unaffected].

New Horizons: Feedbacks from the Stratosphere. A new idea is that during the Ice Ages, the ocean conveyor didn’t shut down but got its new deep water from off Antarctica – so formed a seesaw between the poles? Recently found large lakes of liquid water beneath Antarctic icecap…might set off cascade of fresh water into Southern Ocean similar in scale to emptying of Lake Agassiz that set off the Younger Dryas cold snap?

Other surprises. Arctic Oscillation, the second largest climate cycle after El Nino on Earth…changes in relative air pressures strenghten or weaken the pervailing westerly winds that circle the Arctic. In positive mode, pressure differentials between polar and extra­polar regions are strong and winds strengthen, taking heat from warm oceans and heating the land – northern Europe, Svalbard, Siberia, Alaska and Atlantic coast of N. America. Was strongly positive for last 35 years, and contributed to half of global warming over the Arctic!

But GW is driving the AO itself too, though. Greenhouse gases cool stratosphere → alters energy distribution within stratosphere that enhances winds, inc. the stratospheric jet that swirls around the Arctic in winter  →  drives westerly tropospheric winds faster → warming. Same effect in Antarctica with the Southern Hemisphere Annular Mode.

Important amplifying mechanism, since when solar output changes, the change in UV is very great – but since its stopped by ozone, it has a much bigger effect on the stratosphere than at ground level. (AK: now that might change). Hence causes particular feedbacks over northern regions, e.g. during Maunder Minimum only Europe could really be said to have experienced Little Ice Ages.

Climate skepticism? But this is only amplifier. Though solar output is correlated more or less OK with temps for much of 20th C, the link is decidedly broken after the 1970′s which sees notable cooling with slightly diminished solar radiation.

Related posts:

1. Notes on “Six Degrees: Our Future on a Hotter Planet” (M. Lynas)
2. The Dilemmas of Global Dimming
3. Notes on “The Olduvai Theory” (R. Duncan)
4. The Century without an Indian Summer
5. Notes on “The Collapse of Complex Societies” (J. Tainter)